Multipiece allograft implant

ABSTRACT

An allogenic implant for use in intervertebral fusion is formed from two parts. The first part, composed of cortical bone, provides mechanical strength to the implant, allowing the proper distance between the vertebrae being treated to be maintained. The second part, composed of cancellous bone, is ductile and promotes the growth of new bone between the vertebrae being treated and the implant, thus fusing the vertebrae to the implant and to each other. The implant is sized and shaped to conform to the space between the vertebrae. Teeth formed on the superior and inferior surfaces of the implant prevent short-term slippage of the implant.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of prior patent application Ser. No.10/931,788, filed Sep. 1, 2004, now U.S. Pat. No. 7,226,482 B2, whichclaims priority from U.S. provisional patent application No. 60/499,926,filed Sep. 2, 2003. The entire contents of these applications areexpressly incorporated herein by reference thereto

FIELD OF THE INVENTION

The present invention is directed to an allogenic implant and, moreparticularly, to an allogenic intervertebral implant for the fusion ofvertebrae.

BACKGROUND OF THE INVENTION

A number of medical conditions, such as compression of spinal cord nerveroots, degenerative disc disease, and trauma can cause severe back pain.Intervertebral fusion is a surgical method of alleviating back pain. Inintervertebral fusion, two adjacent vertebral bodies are fused togetherby removing the affected intervertebral disc and inserting an implantthat would allow for bone to grow between the two vertebral bodies tobridge the gap left by the removed disc.

A number of different implants and implant materials have been used forfusion with varying success. Current implants for intevertebral fusioninclude metallic cages and allografts. Metallic cages suffer from thedisadvantage of requiring drilling and tapping of the vertebralendplates for insertion. In addition, the incidence of subsidence inlong term use is not known. Due to MRI incompatibility of metalliccages, determining fusion is problematic.

Allografts are sections of bone taken from the diaphysis of a long bone,such as the radius, ulna, fibula, humerus, tibia, or femur of a donor. Across-section of the bone is taken and processed using known techniquesto preserve the allograft until implantation and reduce the risk of anadverse immunological response when implanted. For example, U.S. Pat.No. 4,678,470 discloses a method for processing a bone grafting materialwhich uses glutaraldehyde tanning to produce a non-antigenic,biocompatible material. Allografts have mechanical properties which aresimilar to the mechanical properties of vertebrae even after processing.This prevents stress shielding that occurs with metallic implants. Theyalso promote the formation of bone, i.e., osteoconductive, and are alsoMRI compatible so that fusion can be more accurately ascertained.Although the osteoconductive nature of the allograft provides abiological interlocking between the allograft and the vertebrae for longterm mechanical strength, initial and short term mechanical strength ofthe interface between the allograft and the vertebrae needs to beaddressed to minimize the possibility of the allograft being expelledafter implantation.

Most allografts are simply sections of bone which, although cut to theapproximate height of the disc being replaced, have not been sizedand/or machined on the exterior surface to have a uniform shape. As aresult, the fusion of the vertebral bodies does not occur in optimalanatomic position or in a consistent manner along the surface of theendplates. While a surgeon may do some minimal intraoperative shapingand sizing to customize the allograft for the patient's spinal anatomy,significant shaping and sizing of the allograft during the procedure isnot possible due to the nature of the allograft. Even if extensiveshaping and sizing were possible, a surgeon's ability to manually shapeand size the allograft to the desired dimensions is limited.

With respect to the overall structure of a given bone, the mechanicalproperties vary throughout the bone. For example, a long bone (leg bone)such as the femur has both cortical bone and cancellous bone. Corticalbone, the compact and dense bone that surrounds the marrow cavity, isgenerally solid and thus carries the majority of the load in long bones.Cancellous bone, the spongy inner bone, is generally porous and ductile,and when compared to cortical bone is only about one-third toone-quarter as dense, one-tenth to one-twentieth as stiff, but fivetimes as ductile. While cancellous bone has a tensile strength of about10-20 MPa and a density of about 0.7, cortical bone has a tensilestrength of about 100-200 MPa and a density of about 2. Additionally,the strain to failure of cancellous bone is about 5-7%, while corticalbone can only withstand 1-3% strain before failure. It should also benoted that these mechanical characteristics may degrade as a result ofnumerous factors such as any chemical treatment applied to the bonematerial, and the manner of storage after harvesting but prior toimplantation (i.e. drying of bones).

Notably, implants of cancellous bone incorporate more readily with thesurrounding host bone, due to the superior osteoconductive nature ofcancellous bone as compared to cortical bone. Furthermore, cancellousbone from different regions of the body is known to have a range ofporosities. Thus, the design of an implant using cancellous bone may betailored to specifically incorporate material of a desired porosity.

There is a need for an allograft that properly utilizes the differentproperties of cortical and cancellous bone to improve stability and topromote growth of new bone to fuse the vertebrae being treated duringintervertebral fusion.

SUMMARY OF THE INVENTION

The present invention relates to an allogenic intervertebral implant foruse when surgical fusion of vertebral bodies is indicated. The implantpreferably comprises a wedge or plug conforming in size and shape withthe end plates of adjacent vertebrae and has a plurality of teethpositioned on the top and bottom surfaces for interlocking with theadjacent vertebrae. The teeth preferably have a pyramid shape or asaw-tooth shape.

The implant preferably is comprised of two or more parts. At least thefirst part is preferably composed of cortical bone, while at least thesecond part is preferably composed of cancellous bone. The implant isconfigured so that when inserted between the vertebrae to be treated,the cortical and cancellous parts of the allograft are positioned sothat the different properties possessed by the cortical and cancellousbone may be utilized effectively. The cortical part of the allograft isaligned with the vertebrae so that it bears the majority of the forcesexerted on the implant, while the cancellous bone section promotes thegrowth of new bone with the implant to allow the vertebrae being treatedto fuse with the allograft and each other.

The two or more sections preferably are attached by a dovetail joint.One or more pins may also be used to prevent the two sections fromsliding out of connection with each other. The pins may be made ofallogenic bone. Preferably the two or more pieces or sections arealigned so that they are side by side when inserted between vertebrae.

The implant preferably has teeth that are formed at least in thecortical section of the allograft. Teeth formed from cortical bone,being much harder and stiffer than cancellous bone, are more effectivein keeping the implant from being displaced. Furthermore, since thecortical part of the implant is where most of the load bearing occurs,teeth formed in this part have the greatest ability to grip into thevertebrae surfaces. Teeth may also be formed in portions of or theentire cancellous bone section or sections.

The implant may take on various profiles and exterior geometries,depending upon the area of the spine that is to be treated. The implantmay further be shaped with various thicknesses, to maintain the properdistance between the vertebrae being treated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary embodiment of the implantaccording to the present invention.

FIG. 2 is a top view of the embodiment of FIG. 1.

FIG. 3 is a back view of the embodiment of FIG. 1.

FIG. 4 is a side view of the embodiment of FIG. 1.

FIG. 5 is a partial top view of the embodiment of FIG. 1.

FIG. 6 is a partial side view of the embodiment of FIG. 1.

FIG. 7 is a top exploded view of the implant of FIG. 1.

FIG. 8 is a side view of a second exemplary embodiment of an implant inaccordance with the present invention.

FIG. 9 is a back view of the embodiment of FIG. 8.

FIG. 10 is a side view of a third exemplary embodiment of an implant inaccordance with the present invention.

FIG. 11 is a back view of the embodiment of FIG. 1.

FIG. 12 is a partial side view of an alternative teeth formation for theimplant of FIGS. 7, 8, and 10.

FIG. 13 is a top view showing representative dimensions of theembodiment of FIGS. 1, 8, and 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a perspective view of a first embodiment of anintervertebral allograft spacer or implant 10 according to the presentinvention. Implant 10 preferably is shaped to conform in size and shapewith at least a portion of the end plates of the vertebrae between whichimplant 10 is to be used. The outer periphery of implant 10 may be sidedand shaped to match the outer periphery of the end plates of thevertebrae between which the implant 10 is to be used. Alternatively theouter periphery of the implant 10 may be sided and shaped to match onlya portion of the outer periphery of the end plates of the vertebrae, orit may have an outer periphery that may not match the peripheral shapeof the end plates of the vertebrae at any location.

Implant 10 generally comprises a superior surface 14, an inferiorsurface 16, and an exterior surface 18. Superior surface 14 and inferiorsurface 16 further may comprise toothed sections 15 and flat sections17. Toothed sections 15 of superior surface 14 and inferior surface 16may be generally of the same size and shape, with toothed sections 15being formed towards anterior end 6 and flat sections 17 being formedtowards posterior end 4.

Implant 10 preferably is formed by the connection of first part 20 andsecond part 30. First part 20 preferably is formed from cortical bone.Second part 30 preferably is composed of cancellous bone. First part 20and second part 30 preferably are connected by a dovetail joint 40 sothat first part 20 and second part 30 are connected side by side to eachother. Second part 30 may comprise a ledge 19 (see FIG. 4) between aflat section and a toothed section of both superior surface 14 andinferior surface 16. First part 20 and second part 30 may furthercomprise first hole 28 and first hole 38 (not shown) through which pin50 may be inserted to prevent sliding of first part 20 and second part30 along dovetail joint 40. First hole 28 may be formed such that itgoes through the entire length of first part 20. Second hole 38 may beformed such that it goes through the entire length of second part 30 oronly a portion thereof. Pin 50 may be inserted through the entirety offirst part 20 and second part 30 or through only a portion thereof. Pin50 may be sized such that pin 50 protrudes from either first hole 28 orsecond hole 38 when pin is fully inserted. In this case, any excessportion of pin 50 protruding from first hole 28 or second hole 38 may beremoved by further processing. Alternatively, pin may be sized so thatit does not extend all the way through both first hole 28 and/or secondhole 38.

As shown in FIG. 7, male portion 42 of dovetail joint 40 may be formedon first part 20, and female portion 44 of dovetail joint 40 may beformed on second part 30. However, in an alternative embodiment, maleportion 42 may be formed on second part 30 and female portion 44 may beformed on first part 20. Male portion 42 may have a length z thatpreferably is approximately 3 mm, a first width x at its narrowest pointthat preferably is approximately 3.1 mm, and a second width y at itswidest point that preferably is approximately 6.3 mm, with femaleportion 44 having corresponding dimensions (see FIG. 13). In analternative embodiment, female portion 44 has dimensions that areslightly smaller than the dimensions of male portion 42, thus creatingan interference fit between male portion 42 and female portion 44.However, it is to be understood that male portion 42 and female portion44 may have different dimensions than the ones described above withoutdeparting from the spirit and scope of the invention. In addition, morethan one dovetail connection, and/or more than one pin connection may beused in forming implant 10. Furthermore, the pin may be inserted inalternative locations. Furthermore, other methods of connecting firstpart 20 and second part 30 may be used without departing from the spiritand scope of the invention.

Implant 10 has a plurality of teeth 12 formed within toothed sections14, 16 that preferably provide a mechanical interlock between implant 10and the end plates of the vertebrae to be treated. Preferably, as shownin FIGS. 5 and 6, teeth 12 may be pyramid shaped, with the angle formedfrom the tip to the base being approximately 60 degrees. Alternatively,teeth 12 may have a saw tooth shape with the saw tooth running in theanterior-posterior direction (see FIG. 12).

As seen in FIGS. 1 to 4, the majority of toothed sections 15 arecomprised of the entire superior surface 14 and inferior surface 16 offirst part 20. Because these teeth 12 are preferably formed fromcortical bone, teeth 12 have sufficient strength and hardness to impalethemselves into the vertebrae surfaces and provide an enhanced interlockwith the adjacent vertebrae. Teeth 12 may also be formed in second part30 in order to simplify the manufacturing process (further describedbelow), although these teeth 12 do not have the same strength andhardness of teeth 12 formed in first part 20.

Teeth 12 are generally arranged in a two-dimensional array or pattern.In a preferred embodiment, teeth 12 are arranged in an array composed ofevenly spaced rows and columns. However, it can be readily seen by thoseskilled in the art that teeth 12 may be arranged within toothed sections15 in many different ways, without departing from the spirit and scopeof the present invention.

Flat sections 17 preferably are comprised entirely upon superior surface14 and inferior surface 16 of second part 30. Flat sections 17, beingformed of cancellous bone, are more ductile that toothed sections 15 andwill deform to conform to the surface contours of the vertebrae beingtreated. This further ensures an optimal fit of implant 10 between thevertebrae and promotes fusion of the vertebrae with the implant 10,without excessive contouring of the surfaces of implant 10.

Ideally, an intervertebral implant comprises as much cancellous bone aspossible while providing sufficient support to maintain the properspacing between the vertebrae being treated, so that the promotion ofnew bone growth is maximized. By properly sizing and shaping firstsection 20 of implant 10, composed of cortical bone, and by properlyaligning first part 20 so that it is subject to the majority of forcesexerted on implant 10 by the vertebrae being treated, implant 10 hassufficient strength to maintain the proper distance between thevertebrae, while minimizing the amount of cortical bone required. Therest of implant 10, being composed of cancellous bone (i.e., second part30), can then be used more advantageously to promote the growth of newbone between the vertebrae being treated, thus providing long-termstability to the vertebrae and implant 10. Because most of the loadbearing of implant 10 occurs on first part 20, the effectiveness ofteeth 12 formed in first part 20 to grip into the surfaces of thevertebrae is enhanced. The application of force on first part 20, andtherefore teeth 12, enhances the ability of teeth 12 to penetrate intoand grip the vertebrae surfaces, thus preventing short-term slippage ofimplant 10 until implant 10 is fused with the vertebrae by the growth ofnew bone.

Thus, implant 10 takes advantage of the different properties of corticaland cancellous bone to improve the use of allogenic bone in the surgicalmethod of intervertebral fusion. Implant 10 may be customized accordingto the needs of the user, as different combinations of cortical andcancellous bone, may be selected, depending upon the properties desired.An implant 10 in accordance with the present invention also allows formore efficient use of available material, as pieces of allogenic bonethat would otherwise not be large enough to form a suitably sizedimplant may be used instead to form a part of implant 10.

In the preferred embodiment shown in FIGS. 1 to 4, superior surface 14and inferior surface 16 are parallel with each other. However, incertain areas of the spine, it may be desirable for implant 10 to haveinclined and/or curved surfaces in order to restore the naturalcurvature of the spine after the affected disc has been removed. Forexample, as shown in FIGS. 8 and 9, implant 220 may have a wedge shapedprofile, with superior surface 214 and inferior surface 216 eachdefining an angle θ. Angle θ may preferably be within the range of about2 to about 5 degrees, and preferably is about 3.5 degrees. In yetanother embodiment, as shown in FIGS. 10 and 11, inferior surface 116defines an angle φ, while superior surface 114 is curved to conform tothe surface of the topography of the vertebral end plates. Angle φ maypreferably be within the range of about 2 to about 5 degrees, andpreferably is about 3.5 degrees. The radius of curvature of superiorsurface 114 may be within the range of about 8 to about 25 mm, andpreferably is about 14 mm.

In the above illustrated embodiments, and as further illustrated in FIG.13, exterior surface 18 is formed so that posterior end 4 is flat, whileanterior end 6 is curved. Anterior end 6 has a radius of curvaturepreferably within the range of about 15 to about 25 mm, and preferablyis about 20 mm. The length L of implant 10 from anterior end 6 toposterior end 4 is preferably within the range of about 10 to about 15mm, and preferably is about 12.5 mm. First part 20 has a length l(including male section 42) preferably within the range of about 4 toabout 8 mm, and preferably is about 6 mm. The width W of implant 10 fromthe medial surface 70 to the lateral surface 72 at its widest point ispreferably within the range of about 10 to about 18 mm, and preferablyis about 15 mm. Furthermore, sides 5 of exterior surface 18 thatcorrespond with toothed sections 15 are parallel to each other, whilesides 7 of exterior surface 18 that correspond with flat sections 17 areangled in towards posterior end 4 at angle α. Angle α is preferablywithin the range of about 20 to about 40 degrees, and preferably isabout 30 degrees. With this geometry, implant 10 may ideally be usedbetween cervical vertebrae. However, it can be readily seen by thoseskilled in the art that exterior surface 18 may take on many differentgeometries to optimize the use of implant 10 between vertebrae indifferent areas of the spine.

Implant 10 is manufactured by first roughly shaping first part 20 andsecond part 30 out of cortical and cancellous allogenic bone. Maleportion 42 and female portion 44 of dovetail joint 40 are then formed infirst part 20 and second part 30 respectively. Holes 28 and 38 for pin50 are also formed in first part 20 and second part 30. Male portion 42is then inserted in female portion 44, and pin 50 is inserted throughholes 28 and 38. If desired, adhesive may be used between first part 20and second part 30. In a preferred embodiment, pin 50 is sized so thatthere is a slight interference between the exterior surface of pin 50and holes 28 and 38. Pin 50 is thus secured in holes 28 and 38 by aninterference fit between pin 50 and holes 28 and 38. Alternatively,adhesive may be used to secure pin 50 into holes 28 and 38. Flatsections 17 of superior surface 14 and inferior surface 16, and exteriorsurface 18 are then shaped into the proper desired form. Finally, teeth12 are formed into superior surface 14 and inferior surface 16. In apreferred embodiment, the shaping of the parts and sections of implant10 is performed by computer-controlled milling. However, alternativemethods of forming the various parts of implant 10 may also be used.

Using the method of manufacture described above, teeth 12 are formed sothat their tips are either at or below the planes defined by thesurfaces of flat sections 17. In other alternative embodiments, teeth 12may be formed so that they extend past the planes of flat sections 17 byfirst forming teeth 12 on superior surface 14 and inferior surface 16before forming flat sections 17. Furthermore, by milling teeth 12 ontothe superior surface 14 and inferior surface 16 of first part 20 beforejoining first part 20 with second part 30, teeth 12 may be formed onlyfrom cortical bone. However, this may increase the complexity of themanufacturing process.

In order to restore the intervertebral space to the proper size afterthe affected disc has been removed, implant 10 has a height, h, sized tomatch the height of the removed disc. Typically for discectomies, h isbetween about 5 mm to about 12 mm, but other heights may be used.

Implant 10 may also be configured for corpectomies. In which case, itshould be noted that implants 10 can be configured so that h would beapproximately 10 to approximately 150 mm. Other heights may also beused. These larger sizes could be used in corpectomy, a surgicalprocedure in which a section of several vertebrae is removed. Implants10 would be inserted in the space created by the removed section ofbone. Due to the nature of corpectomy, an accurate preoperativedetermination of the size of the implant needed is very difficult. Thus,implant 10 may be cut to the proper size by the surgeon. In such cases,the implants 10 preferably would only have teeth 12 on either superiorsurface 14 or inferior surface 16.

A threaded hole (not shown) may be formed on either anterior end 6,lateral surface 72, or medial surface 70 of implant 10 along exteriorsurface 18 to receive an inserter to implant the implant between thevertebrae. Alternatively, an instrument specifically configured to holdimplant 10 by fitting snugly along at least portions of exterior surface18, for example, at anterior end 6 and portions of medial surface 70 andlateral surface 72 of implant 10 may also be used. Other means forinserting implant 10 may be used in addition to or alternatively to themethods described above.

While the embodiments described above comprise parts formed from asingle piece of cortical bone and single piece of cancellous bone, itwill be appreciated that multiple pieces of cortical and/or cancellousbone may be used to form the parts of an implant in accordance with thepresent invention. It will also be appreciated that while theembodiments described above were formed from two parts joined together,an implant formed from more than two parts is also within the spirit andscope of the present invention.

While it is apparent that the illustrative embodiments of the inventionherein disclosed fulfill the objectives stated above, it will beappreciated that numerous modifications and other embodiments may bedevised by those skilled in the art. Therefore, it will be understoodthat the appended claims are intended to cover all such modificationsand embodiments which come within the spirit and scope of the presentinvention.

1. An intervertebral implant for insertion between adjoining vertebra,said implant comprising: a three dimensional body including a superiorsurface sized and configured for contacting at least a portion of one ofsaid adjacent vertebrae, and an inferior surface sized and configuredfor contacting at least a portion of said other of said adjacentvertebrae; said three dimensional body further comprising: a first partformed of cortical bone and a second part formed of cancellous bone,wherein said first and second parts are connected to one another,wherein substantially the entire superior and inferior surfaces of thefirst part comprises a plurality of teeth, and wherein at least one ofsaid superior and inferior surfaces of said second part includes a firstportion and a second portion, wherein said first portion includes aplurality of teeth and said second portion is substantially smooth, saidtoothed first portion of said second part defining a first surface areaand said substantially smooth second portion of said second part definesa second surface area, said second surface area being greater than saidfirst surface area; wherein said substantially smooth superior andinferior surfaces of said second portion of said second part define anupper plane and a lower plane, respectively, said plurality of teethformed on said superior and inferior surfaces of said first part havinga tip portion, said tip portion being sized and configured to be at orbelow said upper and lower planes; and wherein said first and secondparts are connected by at least one dovetail joint, wherein saiddovetail joint includes a male portion and a female portion, said maleportion being receivable within said female portion, each of said firstpart and said second part further comprising at least one hole extendingpartially therethrough and receiving at least one pin to prevent saidfirst part from moving with respect to said second part; at least one ofsaid holes passes through said male and female portions of said dovetailjoint so that at least one of said pins passes through said dovetailjoint to secure said first and second parts to one another, wherein saidmale portion of said dovetail joint is on said first part and saidfemale portion of said dovetail joint is on said second part.
 2. Theimplant of claim 1, wherein said plurality of teeth formed on at leastone of said superior and inferior surfaces of said first part are sizedand configured to provide a mechanical interlock between said implantand said adjacent vertebra and said substantially smooth second portionof said second part is sized and configured to deform in order toconform to said adjacent vertebra.
 3. The implant of claim 1, whereinboth said superior and inferior surfaces of said second part includes afirst portion and a second portion.
 4. The implant of claim 1, furthercomprising a ledge formed on at least one of said superior and inferiorsurfaces of said second part, said ledge residing between said first andsecond portions.
 5. The implant of claim 1, wherein said female portionof said second part has a first dimension and said male portion of saidfirst part has a second dimension, said first dimension being smallerthan said second dimension thus creating an interference fit betweensaid male and female portions.
 6. The implant of claim 1, wherein saidpin has a first diameter and said at least one hole has a seconddiameter, said first diameter being larger than said second diameter sothat an interference fit is created between said at least one pin andsaid at least one hole.
 7. The implant of claim 1, further comprising afirst adhesive for securing said at least one pin to said at least onehole.
 8. The implant of claim 7, further comprising a second adhesivefor securing said first part to second part.
 9. The implant of claim 1,wherein said three dimensional body further includes a posterior end, ananterior end, and first and second side surfaces sized and configured toextend between said anterior end to said posterior end, wherein saidfirst and second side surfaces of said first part are substantiallyparallel with respect to one another and wherein said first and secondside surfaces of said second portion of said second part are angled intowards said posterior end at an angle.
 10. An intervertebral implantfor insertion between adjoining vertebra, said implant comprising: athree dimensional body including a superior surface sized and configuredfor contacting at least a portion of one of said adjacent vertebrae, andan inferior surface sized and configured for contacting at least aportion of said other of said adjacent vertebrae; said three dimensionalbody further comprising: a first part formed of bone and a second partformed of bone; wherein said first and second parts are connected to oneanother by at least one dovetail joint, wherein said dovetail jointincludes a male portion and a female portion, said female portion beingsized and configured to receive said male portion, each of said firstpart and said second parts further comprising at least one holeextending partially therethrough and receiving at least one pin toprevent said first part from moving with respect to said second part; atleast one of said holes passes through said male and female portions ofsaid dovetail joint so that at least one of said pins passes throughsaid dovetail joint to secure said first and second parts to oneanother; wherein said first part is formed of cortical bone and saidsecond part is formed of cancellous bone; said male portion of saiddovetail joint is on said first part and said female portion of saiddovetail joint is on said second part; wherein substantially the entiresuperior and inferior surfaces of the first part comprises a pluralityof teeth, wherein said superior and inferior surfaces of said secondpart includes a first portion and a second portion, wherein saidsuperior and inferior surfaces of said first portion of said second partinclude a plurality of teeth and said second portion of said second partis substantially smooth; said toothed first portion of said second partdefines a first surface area and said substantially smooth secondportion of said second part defines a second surface area, said secondsurface area being greater than said first surface area; and whereinsaid substantially smooth superior and inferior surfaces of said secondportion of said second part define an upper plane and a lower plane,respectively, said plurality of teeth formed on said superior andinferior surfaces of said first part having a tip portion, said tipportion being sized and configured to be at or below said upper andlower planes.
 11. The implant of claim 10, wherein said plurality ofteeth formed on said superior and inferior surfaces of said first partare sized and configured to provide a mechanical interlock between saidimplant and said adjacent vertebra and said substantially smoothportions formed on said superior and inferior surfaces of said secondportion of said second part are sized and configured to deform in orderto conform to said adjacent vertebra.
 12. The implant of claim 10,further comprising a ledge formed on at least one of said superior andinferior surfaces of said second part, said ledge residing between saidfirst and second portions.
 13. The implant of claim 10, wherein saidthree dimensional body further includes a posterior end, an anteriorend, and first and second side surfaces sized and configured to extendbetween said anterior end to said posterior end, wherein said first andsecond side surfaces of said first part are substantially parallel withrespect to one another and wherein said first and second side surfacesof said second portion of said second part are angled in towards saidposterior end at an angle.
 14. An intervertebral implant for insertionbetween adjoining vertebra, said implant comprising: a three dimensionalbody including a superior surface sized and configured for contacting atleast a portion of one of said adjacent vertebrae, and an inferiorsurface sized and configured for contacting at least a portion of saidother of said adjacent vertebrae; said three dimensional body furthercomprising: a first part formed of cortical bone and a second partformed of cancellous bone, wherein said first part is connected to saidsecond part, wherein substantially the entire superior and inferiorsurfaces of the first part comprises a plurality of teeth and whereinsaid superior and inferior surfaces of said second part includes a firstportion and a second portion, wherein said superior and inferiorsurfaces of said first portion of said second part include a pluralityof teeth and said second portion of said second part is substantiallysmooth; wherein said first and second parts are connected by a dovetailjoint, wherein said dovetail joint includes a male portion and a femaleportion, said male portion being receivable with said female portion,each of said first part and said second parts further comprising a holeextending partially therethrough and receiving a pin to prevent saidfirst part from moving with respect to said second part; said holespassing through said male and female portions of said dovetail joint sothat at least one of said pins passes through said dovetail joint tosecure said first and second parts to one another, wherein said maleportion of said dovetail joint is on said first part and said femaleportion of said dovetail joint is on said second part; and wherein saidsubstantially smooth superior and inferior surfaces of said secondportion of said second part define an upper plane and a lower plane,respectively, said plurality of teeth formed on said superior andinferior surfaces of said first part having a tip portion, said tipportion being sized and configured to be at or below said upper andlower planes.
 15. The implant of claim 14, wherein said toothed firstportion of said second part defines a first surface area and saidsubstantially smooth second portion of said second part defines a secondsurface area, said second surface area being greater than said firstsurface area.
 16. The implant of claim 14, wherein said plurality ofteeth formed on said superior and inferior surfaces of said first partare sized and configured to provide a mechanical interlock between saidimplant and said adjacent vertebra and said substantially smoothportions formed on said superior and inferior surfaces of said secondportion of said second part are sized and configured to deform in orderto conform to said adjacent vertebra.
 17. The implant of claim 14,further comprising a ledge formed on at least one of said superior andinferior surfaces of said second part, said ledge residing between saidfirst and second portions.
 18. The implant of claim 14, wherein saidthree dimensional body further includes a posterior end, an anteriorend, and first and second side surfaces sized and configured to extendbetween said anterior end to said posterior end, wherein said first andsecond side surfaces of said first part are substantially parallel withrespect to one another, and wherein said first and second side surfacesof said second portion of said second part are angled in towards saidposterior end at an angle.